Adaptive tone power control in PLC networks

ABSTRACT

In a powerline communications (PLC) network having a first node and at least a second node on a PLC channel utilizing a band including a plurality of tones, based on at least one channel quality indicator (CQI), the first node allocates for a tone map response payload only a single (1) power control bit for each of a plurality of subbands having two or more tones. The power control bit indicates a first power state or a second power state. The first node transmits a frame including the tone map response payload to the second node. The second node transmits a frame having boosted signal power for the tones in the subbands which have the first power state compared to a lower signal power for the tones in the subbands which have the second power state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application and the subject matter disclosed herein claims thebenefit of Provisional Application Ser. No. 61/544,862 entitled“Utilization in Tone Map and TXCOEF” filed Oct. 7, 2011, which is hereinincorporated by reference in its entirety.

FIELD

Disclosed embodiments relate generally to the field of powerlinecommunications (PLC) and, more specifically, to methods of using tonemaps in PLC networks.

BACKGROUND

PLC is a medium for advanced metering infrastructure (AMI) which allowscommunication signals to be sent through an existing powerline, so newcommunication lines are not needed. Current and next generation narrowband PLC are multi-carrier based, such as orthogonal frequency divisionmultiplexing (OFDM)-based in order to obtain high network throughput.OFDM uses multiple orthogonal subcarriers to transmit data over aplurality of frequency selective channels.

In PLC networks, the system has the ability to communicate in both lowvoltage (LV) powerlines as well as high voltage power lines. Whenoperating in a high-voltage powerline the system is able to communicatewith low-voltage powerlines. This means that the receiver on the LV sidemust be able to detect the transmitted signal after it has been severelyattenuated as a result of going through a medium voltage (MV)/LVtransformer. The coupling interface between the PLC device and the MVmedium may be referred to as a MV/LV crossing.

In PLC networks that have MV/LV crossings, data transmission over thefull FCC allowed frequency band may not be feasible due to networkconditions (e.g., noise) so that smaller frequency band portionsreferred to as tone masks (or simply tones), or groups of tones known assubbands, may be used for each particular MV/LV communication link. Atone map generally refers to an allocation of power for a subbandcomprising two or more tones.

Since the set of tones that provide effective communications for aparticular link may vary link-to-link, and as a function of time, thereceiver may not be tuned to the proper set of tones to decode thereceived frame. When nodes are unable to decode the data payload sentover the tones indicated in the received frame, such as indicated in thePHY header referred to as the frame control header (FCH) in the case ofthe IEEE P1901.2 standard (IEEE P1901.2), the node will set theirvirtual carrier sensing (VCS) to the Extended Interframe Space (EIFS)value to account for the largest data payload size transmission allowedin the PLC network.

Multi-Tone Mask (MTM) mode (or “tone masking”) refers to the use ofmultiple tone-masks/subbands to enable nodes in the network to eachselect individual tones within the band utilized by the network fornetwork communications. When operating in MTM mode, only one/set of TMsmay be optimal (typically the lowest noise) for each particularunidirectional/bidirectional link. After each node (device) performs aninitial tone mask scanning, the nodes determine which tones are optimalfor their UL communications (node to router) and for their DLcommunications (router to node).

The transmitter networked device may request an estimation of a channelcondition by setting a selected bit in the PHY Header. The receivernetworked device estimates this particular communication link betweentwo points and chooses optimal PHY parameters. This information is sentback to the transmitter networked device as a tone map response.

Adaptive tone mapping is used to allow the receiver networked device toachieve the greatest possible throughput given the current channelconditions existing between them. To accomplish adaptive tone mapping,the receiver networked device is configured to inform the transmitternetworked device which tones it should use to send data bits on, andwhich tones it should use to send dummy data bits that the receivernetworked device will ignore. The receiver networked device may beconfigured to also inform the transmitter networked device how muchamplification (or attenuation) it should apply to each of the tones.

FIG. 1A depicts the structure of a tone map response message frame 100for adaptive tone mapping for a known G3 PLC network. Frame 100 includesa preamble 101, a frame control header (FCH) 102, and a tone mapresponse data payload 103.

In IEEE P1901.2, the tone map data functions as a specific link controlto avoid tones that have a low signal to noise ratio (SNR) to allow useof only “good” tones that have a relatively high SNR. In G3 FCC with a4.6875 kHz tone spacing, each tone map defines the power level for asubband which has three adjacent tones, where the subbands each span4.6875 kHz*3=14.0625 kHz. For example, with 72 tones in the G3 FCC band,24 tone maps for 3 tone subbands are available to utilize.

FIG. 1B shows the tone mask response message description for a receivernetworked device utilizing G3-PLC/IEEE P1901.2. TXRES is a parameterthat specifies the transmit gain resolution corresponding to one gainstep. TXGAIN is a parameter that specifies to the transmitter networkeddevice the total amount of gain that it should apply to its transmittedsignal. The value in this parameter specifies the total number of gainsteps needed. The receiver networked device computes the received signallevel and compares it to a VTARGET (pre-defined desired receive level).The power difference in dB between the two values is mapped to a 5-bitvalue that specifies the amount of gain increase or decrease that thetransmitter network device applies to the next frame to be transmitted.A “0” in the most significant bit indicates a positive gain value, hencean increase in the transmitter gain, and a “1” indicates a negative gainvalue, hence a decrease in the transmitter gain. A value of TXGAIN=“0”informs the transmitter network device to use the same gain value itused for previous frame.

TM is a parameter that specifies the Tone Map. The receiver networkdevice estimates the link quality of the channel with the granularity ofthe tone map subband and maps each tone map to a one-bit value. A valueof “0” indicates to the transmitter network device that dummy datashould be transmitted on the corresponding sub carrier while a value of“1” indicates that valid data should be transmitted on the correspondingsub-carrier.

TXCOEF is a parameter that specifies transmitter gain for each 10 kHzsection of the available spectrum. The receiver network device measuresthe frequency-dependent attenuation of the channel and may request thetransmitter network device to adjust the transmit power on sections ofthe spectrum that are experiencing attenuation in order to equalize thereceived signal. Each 14.0625 kHz section is mapped to a 4-bit valuewhere a “0” in the most significant bit indicates a positive gain value,hence an increase in the transmitter gain is requested for that section,and a “1” indicates a negative gain value, hence a decrease in thetransmitter gain is requested for that section.

In the G3-PLC/IEEE P1901.2 standard, there can be seen to be a total of32 bits used in 8 TXCOEF fields which provide power control data fortone maps. Each TXCOEF field (4 bits) thus defines the power controllevel for one tone map (and thus its subband having 3 tones).

SUMMARY

Disclosed embodiments recognize for the tone mask response messageformat for G3-PLC/IEEE P1901.2 (shown in FIG. 1B) there are 8 TXCOEFfields (32 bits/(4 bits/tone map)) possible using 32 bits which eachdefine the power control level for a single tone map (with each tone mapdefining the power level for a subband having 3 tones). However, 24 tonemaps exist in G3 FCC band. Therefore, there are not enough bitsavailable in this standard to represent the 24 tone maps that exist inthe G3 FCC band, because to represent 24 tone maps using 4 bits for eachtone map, there would need to be total 24*4=96 bits allocated to TXCOEF.

Disclosed embodiments include solutions which provide more efficient useof the bits in the TXCOEF fields of tone mask response message frames tocontrol power for each tone used by the network, including in oneparticular embodiment methods of using the 32 bits in the TXCOEF fieldsof a tone mask response message to control power for tones in each ofthe 24 tone maps that exist in G3 FCC band. Applied to G3-PLC/IEEEP1901.2, instead of using 4 bits for each tone map power control foreach tone map as shown in FIG. 1B, as disclosed herein, tone map poweris controlled by a single (1) power control bit, where each powercontrol bit defines whether the tone map (which includes 3 tones forG3-PLC/IEEE P1901.2) is in a first power state or a second power state.

Upon receipt of the tone mask response message frame from the firstnode, the second node transmits a frame having boosted signal power forthe tones in the subbands which have the first power state compared to alower signal power for tones in the subbands that have the second powerstate. In one embodiment the lower signal power tones are allocated nopower (and are thus OFF). Disclosed embodiments can generally be appliedto all OFDM-based PLC networks, and will provide advantages forOFDM-based PLC networks which when using their adopted standard lackenough available bits to represent the power in all defined tone mapsthat exist in network's allowed band.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, wherein:

FIG. 1A depicts the structure of a tone map response message frame foradaptive tone mapping for a known G3 PLC network.

FIG. 1B shows the tone mask response message description for a receivernetworked device utilizing G3-PLC/IEEE P1901.2.

FIGS. 2A-C show an example tone mask response message description for areceiver networked device utilizing G3-PLC/IEEE P1901.2, according to anexample embodiment.

FIG. 3 is a block diagram schematic of a communication device having adisclosed modem that implements adaptive tone power control using adisclosed adaptive power control algorithm, according to an exampleembodiment.

FIG. 4 is a flowchart for an example method for adaptive tone powercontrol for PLC communications, according to an example embodiment.

FIG. 5 is a system model depiction of a PLC network for local utilityPLC communications, configured for U.S. deployment, that can utilizedisclosed embodiments at service nodes and/or base nodes, according toan example embodiment.

DETAILED DESCRIPTION

Disclosed embodiments now will be described more fully hereinafter withreference to the accompanying drawings. Such embodiments may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of this disclosure to those having ordinaryskill in the art. One having ordinary skill in the art may be able touse the various disclosed embodiments and there equivalents. As usedherein, the term “couple” or “couples” is intended to mean either anindirect or direct electrical connection, unless qualified as in“communicably coupled” which includes wireless connections. Thus, if afirst device couples to a second device, that connection may be througha direct electrical connection, or through an indirect electricalconnection via other devices and connections.

For disclosed embodiments, instead of using 4 bits for power control forthe tone masks in each tone map in the tone mask response messagedefinitions shown in FIG. 1B, power control for the tones in each tonemap is controlled by a single (1) power control bit. Each power controlbit defines whether the tone map (which includes 2 or more tones) is ina boosted power state, or is in a lower power state (such as OFF in oneembodiment). For example, TXCOEF[0] controls power for tone map [0],shown as TM[0], TXCOEF[1] controls power for TM[1], TXCOEF[2] controlspower for TM[2], etc.

The selection of power state for the power control bits are based on atleast one channel quality indicator (CQI), including one or more ofsignal to noise ratio (SNR), bit error rate (BER), frame error rate(FER) and channel capacity. The first power state is an ON state thatcan be at a predetermined non-zero power level, and the second powerstate can be an OFF state at a zero power level. In one particularembodiment the predetermined power level is a maximum allowed powerlevel in the PLC network. Alternatively the power level for tones in theON state can be set by equally transmitting power over the respectivetransmit subbands.

FIGS. 2A-C show an example tone mask response message format 200according to an example embodiment, that may be used for G3-PLC/IEEEP1901.2 or another OFDM PLC network. Tone mask response message format200 may be used with the tone map response message frame 100 foradaptive tone mapping shown in FIG. 1A. Although the respective TXCOEFfields are all shown in FIGS. 2A-C with the bit when set to 0 defined tomean the tone map is “off”, as noted above disclosed embodiments neednot have the lower power state be an off state.

FIG. 3 is a block diagram schematic of a communication device 300 havinga disclosed modem 304 that implements adaptive tone power control usinga disclosed adaptive tone power control (ATPC) algorithm, according toan example embodiment. Communication device 300 can be used at a servicenode (SN, which includes switch nodes and terminal nodes) or at a basenode (or data concentrator, BN) in the PLC communications network.

Modem 304 includes a processor (e.g., a digital signal processor, (DSP))304 a coupled to an associated memory 305 that that stores code for adisclosed ATPC algorithm. Memory 305 comprises non-transitory machinereadable storage, for example, static random-access memory (SRAM). Inoperation, the processor 304 a is programmed to implement the ATPCalgorithm. Modem 304 includes a timer 307, such as for acknowledgement(ACK) transmission, Carrier Sense Multiple Access/collision avoidance(CSMA)/CA) back-off and data transmission purposes.

The PLC transceiver (TX/RX) 306 is communicably coupled to the modem 304for coupling of the communication device 300 to the shared powerline340. Transceiver 306 facilitates communications with other SNs and theBN on the powerline 340.

When the communication device 300 acts as a receiver, the processor 304a is programmed to implement the ATPC algorithm which is operable forcompiling a first data frame based on at least one CQI, allocating atone map response payload using only a single (1) power control bit foreach of the subbands each having two or more tones, where the powercontrol bits indicate a first power state or a second power state. Theprocessor 304 a also causes the PLC transceiver 306 to transmit framesincluding the tone map response payload to another node acting as atransmitter on the powerline 340.

When the communication device 300 acts as a transmitter, the ATPC codestored in memory 305 includes code for compiling data frames, decodingthe tone map response payload, and for an adaptive transmission powercontrol algorithm. The processor 304 a is programmed to implementdecoding of a disclosed tone map response payload, and the processor 304a causes the PLC transceiver 306 to transmit frames having boostedsignal power for ones of the subbands which have the first power statecompared to a lower signal power for tones in subbands that have thesecond power state to another node acting as a receiver on the powerline340.

The modem 304 is shown formed on an integrated circuit (IC) 320comprising a substrate 325 having a semiconductor surface 326, such as asilicon surface. Memory 305 may be included on the IC 320. In anotherembodiment the modem 304 is implemented using 2 processor chips, such as2 DSP chips. Besides the DSP noted above, the processor 304 a cancomprise a desktop computer, laptop computer, cellular phone, smartphone, or an application specific integrated circuit (ASIC).

Disclosed modems 304 and disclosed communications devices 300 can beused in a PLC network to provide a networked device that in service isconnected to a powerline via a power cord. In general, the “networkeddevice” can be any equipment that is capable of transmitting and/orreceiving information over a powerline. Examples of different types ofnetworked devices include, but are not limited or restricted to acomputer, a router, an access point (AP), a wireless meter, a networkedappliance, an adapter, or any device supporting connectivity to a wiredor wireless network.

FIG. 4 is a flowchart for an example method 400 of adaptive tone powercontrol for PLC in a PLC network utilizing a band including a pluralityof tones, having a first node and at least a second node on a PLCchannel, according to an example embodiment. Step 401 comprises based onat least one CQI, the first node allocating for a tone map responsepayload only a single (1) power control bit for each of a plurality ofsubbands having two or more tones, wherein the power control bitsindicate a first power state or a second power state. Step 402 comprisesthe first node transmitting a frame including the tone map responsepayload to the second node. Step 403 comprises the second nodetransmitting a frame having boosted signal power for tones in thesubbands which have the first power state compared to a lower signalpower for tones in the subbands that have the second power state.

FIG. 5 is a system model depiction of a PLC network 500 for localutility PLC communications, configured for U.S. deployment, that canutilize disclosed embodiments at SNs or BNs, according to an exampleembodiment: LV nodes 105 include meters 110 having disclosed modems 304that implement adaptive tone power control using a disclosed powercontrol algorithm, which during uplink communications transmit usage andload information (“data”) using the low voltage (LV) access networkportion 125 a of powerline 125 through the transformer 120 over the MVnetwork portion 125 b of powerline 125 to one or more medium voltage(MV) routers (also called switch nodes) 130. In turn, each MV router 130forwards this data to the data concentrator (or base station) 140, whichsends the data to the utility company 160 over a telecommunicationbackbone 150. During downlink communications (router 130 to LV node 105)the direction of communications is reversed relative to uplinkcommunications. Data concentrator (or base station) 140 is also shownincluding a disclosed modem 304. The UL and DL may have a differentoptimal TM/sub-band, and thus may be operated using different tones.

The nodes in PLC network 500 in operation have their processorsprogrammed to implement at least one of a receiver ATPC algorithm and atransmitter ATPC algorithm. The receiver ATPC algorithm once implementedby a processor is operable for compiling first data frames, and to useat least one CQI to allocate a tone map response payload using only asingle (1) power control bit for each of a plurality of subbands havingtwo or more tones, where the power control bits indicate a first powerstate or a second power state. The receiver ATPC algorithm causes thePLC transceiver to transmit first frames including the tone map responsepayload to another node on the powerline 125.

The transmitter ATPC algorithm includes code once implemented by aprocessor for compiling second data frames, decoding a disclosed tonemap response payload, and an adaptive transmission power controlalgorithm. The transmitter ATPC algorithm causes the PLC transceiver totransmit second frames having boosted signal power for tones in thesubbands which have the first power state compared to a lower signalpower for tones in the subbands which have the second power state toanother node on the powerline 125.

EXAMPLES

Disclosed embodiments are further illustrated by the following specificExamples, which should not be construed as limiting the scope or contentof this Disclosure in any way.

It is assumed that the tone map subbands that will be used fortransmitting are defined. One of the simplest power allocationalgorithms for implementation at a transmitter node is to transmit equalpower to a receiver node for all the subbands that are ON and toallocate no power for the subbands that are OFF (as defined in a tonemap response payload received from the receiver node) from the totalpower that is allowed in the PLC network. Upon a change in at least oneCQI at some subsequent time, the change in CQI is reflected in amodified tone map response payload received from the receiver node,which defines an updated set of subbands that are ON and OFF. Thetransmitter may then transmit equal power to the receiver node for theupdated set of subbands that are ON and to allocate no power for theupdated set of subbands that are OFF.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this Disclosure pertains havingthe benefit of the teachings presented in the foregoing descriptions,and the associated drawings. Therefore, it is to be understood thatembodiments of the invention are not to be limited to the specificembodiments disclosed. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

We claim:
 1. A method of adaptive tone power control in a powerlinecommunications (PLC) network utilizing a band including a plurality oftones, having a first node and at least a second node on a PLC channel,comprising: based on at least one channel quality indicator (CQI), saidfirst node allocating for a tone map response payload only a single (1)power control bit for each of a plurality of subbands having two or moreof said plurality of tones, wherein said power control bits indicate afirst power state or a second power state; said first node transmittinga frame including said tone map response payload to said second node,and said second node transmitting a frame having boosted signal powerfor ones of said plurality of tones in said plurality of subbands whichhave said first power state compared to a lower signal power for ones ofsaid plurality of tones in said plurality of subbands that have saidsecond power state.
 2. The method of claim 1, wherein said first powerstate is an ON state at a predetermined non-zero power level, and saidsecond power state is an OFF state at a zero power level.
 3. The methodof claim 1, wherein said at least one CQI includes at least one of asignal to noise ratio (SNR), a bit error rate (BER), a frame error rate(FER) and a channel capacity.
 4. The method of claim 1, wherein saidplurality of subbands each include three of said plurality of tones. 5.The method of claim 2, wherein said predetermined non-zero power levelis a maximum allowed power level in said PLC network.
 6. A modem foradaptive tone power control on a powerline communications (PLC) networkutilizing a plurality of tones, including a first node and at least asecond node on a PLC channel, said modem comprising: a processor;wherein said processor is communicably coupled to a memory which storesan adaptive tone power control (ATPC) algorithm including code forcompiling a tone map response message frame including a tone mapresponse payload, and wherein said processor is programmed to implementsaid ATPC algorithm, said ATPC algorithm: based on at least one channelquality indicator (CQI), allocating for said tone map response payloadonly a single (1) power control bit for each of a plurality of subbandshaving two or more of said plurality of tones, wherein said powercontrol bits indicate a first power state or a second power state;wherein said modem is configured for coupling to a PLC transceiver toprovide said tone map response message frame to said PLC transceiver andcause said PLC transceiver to transmit said tone map response messageframe over said PLC channel.
 7. The modem of claim 6, wherein said ATPCalgorithm includes code for decoding said tone map response payload,code for an adaptive transmission power control algorithm and code forcompiling second frames, wherein said processor is programmed toimplement decoding of said tone map response payload, and wherein saidmodem is configured to cause said PLC transceiver to transmit saidsecond frames having a boosted signal power for ones of said pluralityof tones in said plurality of subbands which have said first power statecompared to a lower signal power for tones in said plurality of subbandswhich have said second power state over said PLC channel.
 8. The modemof claim 6, wherein said modem is formed on an integrated circuit (IC)comprising a substrate having a semiconductor surface, wherein saidprocessor comprises a digital signal processor (DSP).
 9. The modem ofclaim 6, wherein said first power state is an ON state at apredetermined non-zero power level, and said second power state is anOFF state at a zero power level.
 10. The modem of claim 6, wherein saidat least one CQI includes at least one of a signal to noise ratio (SNR),a bit error rate (BER), a frame error rate (FER) and a channel capacity.11. The modem of claim 6, wherein said modem is part of a communicationdevice which includes said memory and said PLC transceiver.
 12. Themodem of claim 9, wherein said predetermined non-zero power level is amaximum allowed power level in said PLC network.
 13. A powerlinecommunications (PLC) network utilizing a band including a plurality oftones, comprising: a first node and at least a second node on a PLCchannel; said first node including a first memory which stores code fora receiver adaptive tone power control (ATPC) algorithm including codefor compiling a first data frame, a first modem coupled to said firstmemory, said first modem comprising: a first processor programmed toimplement said receiver ATPC algorithm and said compiling said firstdata frame, said receiver ATPC algorithm based on at least one channelquality indicator (CQI) allocating a tone map response payload only asingle (1) power control bit for each of a plurality of subbands havingtwo or more of said plurality of tones, said power control bitsindicating a first power state or a second power state; and a first PLCtransceiver communicably coupled to said first modem, said receiver ATPCalgorithm causing said first PLC transceiver to transmit said first dataframe including said tone map response payload to said second node, andsaid second node including a second memory which stores a transmitterATPC algorithm including code for compiling a second data frame,decoding said tone map response payload, and an adaptive transmissionpower control algorithm, a second modem coupled to said second memory,said second modem comprising: a second processor programmed to implementsaid decoding of said tone map response payload, and a second PLCtransceiver communicably coupled to said second modem, said adaptivetransmission power control algorithm causing said second PLC transceiverto transmit said second data frame having boosted signal power for onesof said plurality of tones in said plurality of subbands which have saidfirst power state compared to a lower signal power for ones of saidplurality of tones in said plurality of subbands which have said secondpower state to said first node.
 14. The PLC network of claim 13, whereinsaid first power state is an ON state at a predetermined non-zero powerlevel, and said second power state is an OFF state at a zero powerlevel.
 15. The PLC network of claim 13, wherein said predeterminednon-zero power level is a maximum allowed power level in said PLCnetwork.
 16. The PLC network of claim 13, wherein said at least one CQIincludes at least one of a signal to noise ratio (SNR), a bit error rate(BER), a frame error rate (FER) and a channel capacity.